How do you lock down a city like Boston and how much does it cost?

A SWAT team member scouts the perimeter of South Station on April 19, 2013 in Boston, Mass. South Station was shut down and heavily guarded with police in response to the early morning shootings in Cambridge and Watertown.

Massachusetts Gov. Deval Patrick made the call early this morning, and quickly -- and systematically -- the lockdown was underway.

Peter Boynton, co-director of the Kostas Research Institute for Homeland Security at Northeastern University, says the fact that a lockdown of this size happened so fast and so smoothly is because of investments at the federal, state and local levels made after the terrorist attacks on Sept. 11, 2001.

“Additional and helpful equipment, staffing and personnel, and then also, training and exercising,” Boynton says.

New emergency notification systems, like “ALERTBoston,” got the word out city-wide, but also at the neighborhood level, by e-mail and text message. Law enforcement used social media and electronic billboards. They went through photos and videos from hundreds of surveillance cameras across the greater Boston area. And all that costs money.

“Typically, equipment of this sort, in the post-9/11 era, has been paid for, to a large degree, by federal grants,” Boynton explains.

Those grants also paid for personnel and improving how first responders communicate.

Brian Jackson is a security analyst with the RAND Corporation who marvels at the scale and the scope of this operation, and the technology involved.

“You can only imagine the tactical communication that is required to coordinate searches of this magnitude,” he says.

When the accountants add all this up -- and it won’t be for a while, Jackson says, the biggest line item isn’t going to be equipment, it’s going to be the manhunt.

“The price tag for the operation itself is measured in the overtime and the costs paid to have all of those people out and doing the searching,” he says.

Over time, he says, that’s going to cost millions.

Peter Judge, a spokesman for the Massachusetts Emergency Management Agency, said ballparking the price tag of the equipment, the training and the thousands of police officers was not a concern.

“It’s going to be a very big number, but right now, we’re not worried about what the costs are.”